Technical Field
The present invention relates to a method for feeding electric power into an electric supply network by means of a wind park. The present invention moreover relates to a corresponding wind park.
Description of the Related Art
The feeding of electric power by means of a wind park comprising several wind turbines is a matter of common knowledge. Here, several wind turbines of a wind park are combined in terms of their function, and they feed into the electric supply network through, in particular, a common network feeding point, also referred to as network connection point or PCC (point of common coupling). The wind park has often a park control or park control unit, which realizes common tasks for the wind park. This may include, for example, transmitting information between a network operator and a wind turbine or implementing an external power parameter for the active power to be fed in.
What is furthermore known today is that wind turbines, including wind parks, participate actively in the so-called network support of the respective electric supply network. This includes contributing to stabilizing the voltage within the electric supply network. This also includes taking stabilizing measures in the event of a system incident, such as a network short circuit. Often, such properties of the wind park or wind turbines are specified in the interconnection rules of the operator of the electric supply network (network operator) and may have to be evidenced by the operators of the wind park or wind turbines.
A park control is shown, for example, in U.S. application U.S. 2006 0142899 A1. Network support methods are described, for example, in DE 197 56 777, U.S. Pat. No. 6,965,174 and U.S. Pat. No. 7,462,946.
The power fed in at the network connection point, and thus the energy fed in at the network connection point—or, more precisely, the phase currents fed in—consist of the currents generated by the individual wind turbines. It is hence the wind turbines that generate and provide, by amount and phase, the respective currents and thus the fed-in total current. With modern wind turbines, this is done by using one or more frequency inverters. This means that the wind turbines also take the respective network stabilization and network support measures. What is difficult here, in particular, is to have the wind turbines, in particular the wind parks, meet the increasing demands on network support. It can also be difficult to prove the required network support property.
What can be particularly difficult is the quick implementation of a network support measure in the event of a voltage drop. Here, it is difficult to quickly determine a system incident, in particular a drop in line voltage, and to quickly take network support measures in the event of a corresponding system incident. Suggestions for a quick measurement were already described in U.S. 20120169059 A1. This already makes it possible to very quickly determine a state of the network and record, in particular, the line voltage. Nevertheless, it can remain difficult to quickly take measures in case of a system incident.